This invention relates to new bar soaps which contain anionic surfactants of the fatty acid polyglycol ester sulfate and fatty acid salt type as key components.
Modern bar soaps, more especially toilet soaps, are normally based on mixtures of bovine tallow and coconut oil in a ratio of about 9:1. This fatty mixture is hydrolyzed by addition of sodium hydroxide to the basic soap to which other additives, for example moisturizers, fillers and binders, superfatting agents, dyes and perfumes, etc., are added. Standard toilet soaps contain about 80% fatty acid salts, 10% water and auxiliaries and additives to 100%. The large number of products available to the consumer reflect the keen market interest, but nevertheless make it clear that there is a constant need among consumers for further improved products which are distinguished in particular by improved dermatological compatibility, greater foaming power, greater creaminess, improved refatting, rinse-off behavior, skin feel and the like. By contrast, soap manufacturers are looking for soap formulations which lead, for example, to bars with greater fracture resistance or which allow certain surfactants, for example alkyl sulfates, to be incorporated without difficulty. An overview on this subject can be found, for example, in J. Am. Oil. Chem. Soc. 59, 442 (1982).
So far as the manufacture of bar soaps is concerned, it is possible to look back on a very large number of processes from the prior art. A distinction has to be made in this regard between synthetic "soap-free" soaps, so-called syndets, and in particular combinations of fatty acid salts and synthetic surfactants ("combination bars"). According to EP-A 0 176 330 (Unilever) for example, combination bars are produced by combining fatty acid soaps with salts of isethionic acid. The use of fatty acid isethionates as a synthetic constituent of combination bars is known from EP-A 0 189 332, EP-A 0 472 320 and EP-A 0 508 006 (Unilever).
However, there is a constant need on the market for products with improved properties. In particular, there is a demand for bar soaps which produce a richer and creamier foam than known products and which, in addition, show improved dermatological compatibility. In addition, the soaps should leave the skin with an improved feel and should have a reduced tendency to take up water and to develop cracks. Accordingly, the problem addressed by the present invention was to provide bar soaps that would satisfy the complex requirement profile mentioned above.